1. Field of the Invention
The invention relates to transparent sunscreen gels comprising silicone oil, polyoxyalkylene-organopolysiloxanes, water, a component chosen from alcohols and/or polyols and at least one UV absorber soluble in the aqueous or the oily phase.
2. Description of the Related Art
Transparent emulsions comprising polyol and water/silicone are known and are used, for example, as antiperspirants or hair gels. Matching the refractive index of the aqueous phase to that of the oil phase using polyols, such as glycerol, polyglycerol, propylene glycol, hexane glycol and other polyols, gives transparent emulsions, also called gels. These products are usually prepared using silicone emulsifiers, in which case the oil phase comprises mainly cyclomethicones (cyclic polydimethylsiloxanes) or low molecular weight silicone oils (linear polydimethylsiloxanes).
EP 0 176 884 B1, which corresponds to U.S. Pat. No. 4,698,178 and is herein incorporated by reference, describes the use of polyoxyalkylene-siloxane copolymers containing long-chain alkyl radicals bonded to silicon atoms as emulsifiers for the preparation of W/O emulsions. In particular, this patent specification relates to the use of copolymers of average formula (I) ##STR2## where R is an alkyl radical having from 1 to 4 carbon atoms or a hydrogen radical,
n=10 to200, PA0 m=1 to 25 and PA0 o=1 to 100 with the proviso that, in the average molecule, o.gtoreq.m and 3o&lt;n, PA0 p=7 to 17, and PA0 the molar mass of the residue (C.sub.2 H.sub.4 O--).sub.x --(C.sub.3 H.sub.6 O--).sub.y R is from 250 to 2000, where x and y are chosen such that the weight ratio of oxyethylene groups to oxypropylene groups is from 100:0 to 20:80, PA0 as emulsifiers for the preparation of W/O emulsions, the oily phase of which consists of silicone oil or comprises it, in amounts of from 0.3 to 5% by weight, based on the total weight of the emulsion. PA0 m=2 to 4, PA0 x=3 to 100, PA0 y=0 to 50 PA0 R.sup.1 =H, CH.sub.3,CH.sub.2 CH.sub.3, PA0 n=50 to 200, PA0 as emulsifier in W/O emulsions in amounts of from 0.1 to 20% by weight, based on the total weight of the emulsion. PA0 A is chosen from the group consisting of methyl, phenyl or poloxyalkylene groups of the formula EQU --C.sub.3 H.sub.6 O(C.sub.2 H.sub.4 O).sub.a (C.sub.3 H.sub.6 O).sub.b R', PA0 where R' is chosen from the group consisting of hydrogen, an acyl group or an alkyl group having from 1 to 4 carbon atoms, PA0 a is an integer in the range from 5 to 50 PA0 b is an integer in the range from 5 to 50, PA0 m is an integer in the range from 50 to 1000 and PA0 n is an integer in the range from 1 to 40, and PA0 n=10 to200, PA0 m =1 to 25 and PA0 o=1 to 100 with the proviso that, in the average molecule, o.gtoreq.m and 3o &lt;n, PA0 p=7 to 17, and PA0 the molar mass of the residue (C.sub.2 H.sub.4 O--).sub.x --(C.sub.3 H.sub.6 O--).sub.y R is from about 250 to about 2000, where x and y are chosen such that the weight ratio of oxyethylene groups to oxypropylene groups is from 100:0 to about 20:80, PA0 m=2 to 4, PA0 x--3 to 100, PA0 y=0 to50, PA0 R.sup.1 =H or alkyl, PA0 n=50 to 200, PA0 and/or polyoxyalkylene-organosiloxanes of the formula (III): ##STR7## where R is alkyl or aryl group, PA0 A is chosen from the group consisting of alkyl, aryl or poloxyalkylene groups of the formula --C.sub.3 H.sub.6 O(C.sub.2 H.sub.4 O).sub.a (C.sub.3 H.sub.6 O).sub.b R', PA0 where R' is chosen from the group consisting of hydrogen, an acyl group or an alkyl group having from 1 to 4 carbon atoms, PA0 a is an integer in the range from 5 to 50, PA0 b is an integer in the range from 5 to 50, PA0 m is an integer in the range from 50 to 1000 and PA0 n is an integer in the range from 1 to 40.
Similar .alpha.,.omega.-polyether-polysiloxanes are known as W/O emulsifiers from EP 0 819 426 A2, herein incorporated by reference. This patent application relates to the use of copolymers of the formula (II) ##STR3## where R=--(CH.sub.2 --).sub.m O--(C.sub.2 H.sub.4 O--)x(C.sub.3 H.sub.6 O--).sub.y R.sup.1
Furthermore, EP 0 568 102 A1, herein incorporated by reference, discloses silicone gel compositions which comprise
(a) a silicone oil,
(b) a polyoxyalkylene-organopolysiloxane of the general formula (III) ##STR4## where R is a methyl or phenyl group,
(c) water.
Conventional sunscreen gels, also called balms, are opaque, emulsion-like hydrogels based on polyacrylates or on hydrocolloids, such as cellulose derivatives or xanthan gum, in most cases in combination with polyacrylates, whose alkyl-modified derivatives have a certain emulsifying action.
Example 1 of EP 0 568 102 A1 describes a sunscreen gel which comprises a silicone oil, an organopolysiloxane, water and one part by weight of a UV absorber Escalol.RTM.507. The gel is a water-insoluble, oil-soluble sunscreen filter, namely octyldimethyl PABA. The extremely small amount of sunscreen filter effects only a low sunscreen action. The product Piz Buin Classic Brown Hydro Gel, available commercially from Johnson & Johnson, has the following composition: water, cyclomethicone (and) dimethicone copolyol, glycerol, alcohol, propylene glycol, phenylbenzimidazolsulfonic acid (water-soluble filter), tetrahydroxypropylethylenediamine benzophenone-4 (water-soluble UV filter), fragrances and aroma substances, hyaluronic acid, sodium hydroxide, C.I. 15510, C.I. 47005 (yellow-brown color).
This product corresponds to a transparent W/Si emulsion. The consistency is viscous. The emulsion, referred to as hydrogel, is available in brown squeezable tubes. No cosmetic oils (ester oils, triglycerides) are present and only water-soluble filters are used. The emulsifier "cyclomethicone (and) dimethicone copolyol", which corresponds to the competitor product DC 3225 C from Dow Corning, is unable to stabilize the abovementioned oils or oil-soluble filters. This example has a sun protection factor of 8 in accordance with DIN.
However, if the amount of sunscreen filter is increased, a major change in the refractive index takes place. This means that the gel looses the desired transparency.